Editing Legnano (section)

=== Hydrography ===
[[File:Olona river Legnano.JPG|thumb|left|The [[Olona]] River in Legnano.]]

Legnano is crossed by the [[Olona]] River, which cuts Legnano into two nearly equally sized portions. The Olona has a number of deviations both natural, such as the {{ill|Olonella|it}}, located near [[Visconti Castle (Legnano)|Visconti Castle]], and artificial. The latter of these are the diversionary channels and [[levee]]s that encase much of the river as it flows through Legnano, especially around the former {{ill|Cantoni cotton mill|it|Cotonificio Cantoni|lt=Cantoni}} and {{ill|Dell'Acqua cotton mill|it|Cotonificio Dell'Acqua|lt=Dell'Acqua}} cotton mills.

These were built because the Olona was prone to damaging [[flood]]s,{{sfn|Macchione|Gavinelli|1998|pp=26, 49}}{{sfn|D'Ilario|Gianazza|Marinoni|Turri|1984|pp=188–95}} but consequently made the Olona one of the most [[Water pollution|polluted rivers]] in Italy. The pollution of the river is gradually lessening, however,<ref>{{cite web|title=L'Olona, fiume dell'EXPO, adesso può tornare a vivere|url=http://www.consorziofiumeolona.org/dettaglio.asp?id_articolo=374&id_categoria=Rassegna%20stampa|language=it|website=consorziofiumeolona.org|access-date=9 May 2014}}</ref><ref>{{cite web|title=Piano di governo del territorio 2010|url=http://www.comune.legnano.mi.it/get_content/getfile.cfm?id=6661|language=it|website=legnano.mi.it|publisher=City of Legnano|format=CFM|access-date=9 May 2014}}</ref> while the last damaging flood occurred on 13 September 1995,<ref>{{cite news|last=Rotondo|first=Roberto|title=Maltempo, Varese sott'acqua – Esonda l'Olona|url=https://milano.corriere.it/notizie/cronaca/14_luglio_29/esonda-lago-varese-sott-acqua-sindaco-non-usate-l-auto-d945c56e-172d-11e4-ad95-f737a6cb8946.shtml|work=Milano Corriere|date=29 July 2014|language=it|access-date=30 July 2014}}</ref> and the last in chronological order occurred in July 2014.<ref>{{cite web|url=http://milano.corriere.it/notizie/cronaca/14_luglio_29/esonda-lago-varese-sott-acqua-sindaco-non-usate-l-auto-d945c56e-172d-11e4-ad95-f737a6cb8946.shtml|title=Maltempo, Varese sott'acqua – Esonda l'Olona|date=29 July 2014|access-date=30 July 2014}}</ref>

For the vast majority of the city's stretch, the waterway is pernilted into [[levee]] or stone embankments, which were built to minimize flooding. The Olona, before the construction of embankments and [[drainage]] channels, was in fact a river that scourged with frequent floods the areas it crosses.{{sfn|Macchione|Gavinelli|1998|p=49}}

In the past there were deviations of the course of the river: natural, such as the Olonella, and artificial, such as the canals and the disclaimed by the peasants. The latter were necessary to reach, for [[irrigation]] purposes, the land farthest from the Olona. The extraction of water from the river, and more generally the activities related to the exploitation of the Olona, were regulated, over the centuries, by contracts and regulations.{{sfn|D'Ilario|Gianazza|Marinoni|Turri|1984|pp=188–195}}